ORIGINAL RESEARCH article
Front. Vet. Sci.
Sec. Veterinary Pharmacology and Toxicology
This article is part of the Research TopicInnovations in Pharmacotherapy: Developing Novel Medicines for the Treatment of Animal DiseasesView all articles
In vitro Antibacterial Activity and Mechanism of Cell-free Supernatant of Bacillus velezensis Ea73 against Streptococcus agalactiae, a predominant bacteria that causes mastitis in cows
Provisionally accepted
- 1Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China
- 2Institute of Animal Husbandry Sciences of Ganzi Tibetan Autonomous Prefecture No. 926, Kangding, China
Select one of your emails
You have multiple emails registered with Frontiers:
Notify me on publication
Please enter your email address:
If you already have an account, please login
You don't have a Frontiers account ? You can register here
Streptococcus agalactiae (S. agalactiae or GBS) is the main pathogen causing subclinical mastitis in dairy cows. This infection has seriously affected the development of the global dairy industry and thus requires urgent mitigation strategies to reduce its spread. Thus endophytes which are potential sources of novel bioactive antibacterial compounds can effectively be harnessed to address the issues of bacterial infections and resistance in animal production. The aim of this study was to investigate the in vitro antibacterial activity and potential mechanism of Bacillus velezensis Ea73 (an endophyte from Ageratina adenophora plant) cell free supernatant (CFS) against S. agalactiae isolated from cows. The antibacterial activity of Ea73 CFS against S. agalactiae was analyzed by plate and double dilution methods. Biofilm staining and transmission electron microscopy wereas used to explore the effects of Ea73 CFS on biofilm formation, structure and extracellular polymeric substances in the S. agalactiae. In addition, network pharmacology was used to further explore the relevant mechanisms of Ea73 CFS in treating diseases mediated by S. agalactiae. The results showed that the inhibition zone diameter of Ea73 CFS against S. agalactiae was 12 mm, and the minimum biofilm inhibition concentration was 10 mg/mL. After treatment with Ea73 CFS, the biofilm formation was significantly inhibited, the structure of the generated biofilm was disrupted, and the metabolic activity of bacterial cells wasere significantly reduced. The results from this study indicated that EA73 CFS significantly inhibits S. agalactiae activity via biofilm eradication and hence can serve as a promising antibacterial reagent.
Keywords: Bacillus velezensis Ea73, Streptococcus agalactiae, In vitro antibacterial activity, Biofilm formation, Cell free supernatant
Received: 09 Aug 2025; Accepted: 21 Oct 2025.
Copyright: © 2025 Peng, Okyere, Cheng, Tang, Yang, Liu and HU. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Yanchun HU, hychun114@163.com
Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.